Nadine can be found inside the Ark & Dove cathedral once the quest Walking with Spirits is completed. She is now a member of the local tribe but not all that thrilled by it. She tells you about someone cutting portions of the contestants' brains out during the ritual. She wants to meet up with you at Point Lookout Pier once she has confirmed her suspicions regarding who that might be.

When you meet her there, she reveals that Tobar is the one who is collecting brain portions and that she will take the Duchess Gambit as compensation for what he has done. Now she agrees to meet her mother back in the Capital Wasteland and you are no longer charged for using the ship.

ps3xbox360 It's possible for Catherine to "disappear" when you return to the Capital Wasteland. This is likely to happen if Catherine is fleeing when you leave the first time causing her to "flee" out into the surrounding wastes making the quest near impossible to complete. [verified]